Various forms of membranes and thin films find numerous industrial and commercial uses. For example, these materials are frequently used in separation processes, including water treatment, reverse osmosis, pervaporation, dialysis, solvent extraction, and gas permeation methods. In addition, films are used in many commercial devices, such as photovoltaics, electronics, electrodes, and batteries to provide beneficial physical properties and/or electrical properties.
However, the performance, life, and ultimately the cost of films depend heavily on how they are manufactured. For example, to be economically viable, manufacturing processes often need to be large-scale and operated continuously in order to take advantage of economies of scale. In addition, industrial manufacturing processes must be able to reliably and consistently meet minimum quality standards to maximize the manufacturing plant's production rates, to minimize recycle and waste, and to insure the quality and performance of the final manufactured items.
The quality and performance of films depend heavily on the quality and characteristics of materials that are used to construct them. For example, often interrelated physical properties such as density, porosity, thermal conductivity, electrical conductivity, heat capacity, and multi-phase homogeneity or heterogeneity, may all significantly impact how films perform in their final intended applications. In addition, physical defects within the films and/or at their surfaces, for example scuffs, scores, slits, bubbles, pinholes, bubbles, agglomerates, occlusions and/or other bulk and/or surface inhomogeneities may be especially detrimental to film performance. Once the occurrence of such defects reach a certain critical threshold, the manufacturing process may become inefficient and costly. To avoid potential shutdowns, to minimize production costs, and to maximize product quality, on-line methods have been developed to detect, identify, and/or quantify film quality issues. However, many of the methods developed to date remain unreliable, difficult to use in a manufacturing environment, costly, and/or are unable to detect the size, shape, and/or density of film defects.
For these reasons, it is apparent that there exists a need for fast, reliable, non-destructive, and cost-effective, online evaluation of thin films, membranes and electrodes, especially for large-scale, continuous manufacturing environments. Development of such methods may in turn enable new emerging technologies that utilize films and membranes and electrodes to better compete with incumbent technologies, from both performance and economic perspectives.